This invention relates to a carburetor idle port valve for internal combustion engines. The valve is used for controlling the air and fuel mixture in the carburetor during such periods as the throttle is in closed position, and the engine is fed fuel only through the idle port and jet. Devices of this general type are well known in the art, and the invention lies in specific constructional details which permit sensitive operation without need for overriding manual control, while maintaining the cost of manufacture at a very reasonable level.
The idling system in a carburetor supplies a small quantity of an air and fuel mixture to keep the engine running when the throttle is closed or nearly closed. As the throttle is opened, an increased suction is applied to the idling system and more fuel is supplied thereby. An increased suction is likewise applied to the main fuel discharge nozzle as the throttle is opened and fuel is discharged therefrom with a gradual reduction in discharge from the idle system until the discharge in the idle system is neglible. The discharge from the idling system, when transferring to the main discharge system as the throttle is being opened, or when the throttle remains only partly open, is normally overenriched as the idling system is normally calibrated at one specific position.
Overenrichment of the fuel system of a carburetor can and has brought about undesirable results. A simple overenrichment results in a waste of fuel and thus, a loss in economy of operation. More importantly, in recent years, the presence of unburned hydrocarbons in the exhaust gases from automotive engines have been found to contribute to an undesirable atmospheric condition more commonly called "smog". It is generally understood that too rich a fuel mixture may easily result in incomplete burning, due to lack of sufficient oxygen, which, in turn, results in the discharge of unburned hydrocarbons and incomplete combustion of other hydrocarbons to produce carbon monoxide.
In present day automotive carburetors, the only adjustment normally available is the idle fuel needle screw wherein the needle adjustment is set to give smooth operation at curb idle. It is known to provide in the aftermarket, devices such as that disclosed in U.S. Pat. No. 3,348,823, to Roquerre and U.S. Pat. No. 3,077,341 to Schlichting which supplement normal needle valve adjustment with a resilient check valve which becomes operative during periods of high vacuum. At the present time, such devices are useful only in those automobiles which are equipped with carburetors, as distinguished from fuel injection devices. Such cars are substantially older, and are characterized by normal high fuel consumption and relatively little net worth. With the recently occurring increases in the cost of fuel, it becomes highly desirable to provide a device of this type which can be manufactured at very low cost and which is easily installed.